Method startWrite

deps/physx/physx/source/physx/src/NpScene.cpp:2615–2659

#if NP_ENABLE_THREAD_CHECKS

NpScene::StartWriteResult::Enum NpScene::startWrite(bool allowReentry)
{ 
	PX_COMPILE_TIME_ASSERT(sizeof(ThreadReadWriteCount) == 4);

	if (mScene.getFlags() & PxSceneFlag::eREQUIRE_RW_LOCK)
	{
		ThreadReadWriteCount localCounts(TlsGetValue(mThreadReadWriteDepth));

		if (mBetweenFetchResults)
			return StartWriteResult::eIN_FETCHRESULTS;

		// ensure we already have the write lock
		return localCounts.writeLockDepth > 0 ? StartWriteResult::eOK : StartWriteResult::eNO_LOCK;
	}
	
	{
		ThreadReadWriteCount localCounts(TlsGetValue(mThreadReadWriteDepth));
		StartWriteResult::Enum result;

		if (mBetweenFetchResults)
			result = StartWriteResult::eIN_FETCHRESULTS;

		// check we are the only thread reading (allows read->write order on a single thread) and no other threads are writing
		else if (mConcurrentReadCount != localCounts.readDepth || mConcurrentWriteCount != localCounts.writeDepth)
			result = StartWriteResult::eRACE_DETECTED;
		
		else
			result = StartWriteResult::eOK;

		// increment shared write counter
		Ps::atomicIncrement(&mConcurrentWriteCount);

		// in the normal case (re-entry is allowed) then we simply increment
		// the writeDepth by 1, otherwise (re-entry is not allowed) increment
		// by 2 to force subsequent writes to fail by creating a mismatch between
		// the concurrent write counter and the local counter, any value > 1 will do
		localCounts.writeDepth += allowReentry ? 1 : 2;
		TlsSetValue(mThreadReadWriteDepth, localCounts.getData());

		if (result != StartWriteResult::eOK)
			Ps::atomicIncrement(&mConcurrentErrorCount);

		return result;
	}
}

void NpScene::stopWrite(bool allowReentry) 
{